Explanation:
Why do some places on Earth have higher gravity than others?
Sometimes the reason is unknown. To help better understand the
Earth's surface, slight distance changes between a
pair of identically orbiting satellites named
GRACE
have been used to create the best ever map of Earth's
gravitational field.
High points on
this
map, also colored red, indicate areas where gravity is
slightly stronger than usual, while in blue areas gravity is
slightly weaker.
Many bumps and valleys on the map can be
attributed to surface features, such as the
North
Mid-Atlantic Ridge and the
Himalayan Mountains,
but others cannot, and so might relate to unusually
high or low sub-surface densities.
Maps
like this also help calibrate changes in the
Earth's surface including
variable ocean currents and the
melting of glaciers.